Method of refining copper



Patented Dec. 21, 1937 UNITED STATES PATENT OFFICE METHOD or asrmno COPPER No Drawing. Application August 7, 1936, Serial No. 94,797

6 Claims.

This invention relates to a method of refining copper and more particularly to a method of removing lead and other impurities from secondary copper.

In the ordinary refining of primary copper the removal of lead is not involved because no appreciable amount of lead is present in the usual sources of copper. However, in reclaimed or secondary copper, lead is ordinarily present from 10 soldered joints or lead sheathing of copper wire and frequently it enters as tramp metal overlooked in sorting the scrap.

An object of the invention is to provide an effective and efficient method of removing lead 10 and other impurities from copper.

In accordance with one embodiment of the invention, lead and other impurities are oxidized in a molten copper bath and the oxidized lead is volatilized by maintaining the temperature of 2 the bath in a definite range and keeping the surface of the bath free from slag.

Other objects and advantages will appear as the description proceeds.

In practicing the invention, the copper to be 25 refined is melted in a reverberatory furnace and is oxidized by blowing or' forcing air into the melt through an iron pipe. No slag is used during the oxidation and such slag as is formed by corrosion of the furnace lining, the oxidation of 30 the impurities in the copper, and the oxidation of the iron introduced into the melt by the burning away of the iron pipe used in introducing the air is removed from the surface to keep the surface substantially free from slag. The sur- 35 face is, therefore, exposed directly to the sweep of the oxidizing furnace gases which, together with the introduction of the air into the bath, causes the oxygen content of the bath to increase rapidly to promote the formation of lead 40 oxide.

During the first portion of the period of oxidation the temperature of the bath is maintained at substantially 2050 F. because it appears that the oxidation of the copper proceeds more rapid- 45 ly at this temperature than at higher temperatures. This portion of the oxidizing cycle may require two or more hours depending upon the amount of lead or other impurities in the copper.

59 During the last half of the oxidizing cycle the temperature of the bath is raised to approximately 2160 F. in order to increase the rate of volatilization of the lead oxide. From the fact that volatilization of lead does not take place 55 when the oxygen content of the bath is low, it

appears that removal of lead from the bath is accomplished by the volatilization of an oxide of After a chemical analysis indicates that the lead content is within permissible limits, it is advisable to remove small remaining amounts of iron resulting from the consumed blow pipe and from other contamination. This is done by adding a suitable slag such as raw dolomite and. after approximately thirty minutes the bath is skimmed free of all slag.

Poling of the copper up to pitch for casting is then effected under a cover of charcoal until samples taken in a test ladlev indicate by the 2 manner of solidification and set, that the oxygen content has been reduced to the desired value, which for some purposes may be about .05%. The poling of the copper may be more efficiently accomplished by reducing the temperature to approximately 2080 F. In cases where the copper to be treated contains a very large amount of lead it is advisable to alternately oxidize and pole the copper. Thus, for instance, the copper may be oxidized for twohours at the oxidation temperature and lead oxide volatilized for a period of two hours at the volatilization temperature. The copper may then be poled until a dark spot appears upon a specimen withdrawn in a small test ladle, and then the copper is again subjected to an oxidation and volatilization. This process may be repeated several times if a large amount of lead is present in the copper to be refined.

It will be understood that the nature and embodiment of the invention disclosed is merely il- 40 lustrative and that many changes and modifications may be made therein without departing from thespirit and scope of the invention.

What is claimed is:

1. The process of removing lead from copper which comprises heating molten copper to the optimum oxidizing temperature, introducing an oxidizing medium into the bath, raising the temperature to the optimum volatilization temperature of lead oxide, and keeping the surface of the bath substantially free from slag during the mentioned steps.

2. The process of removing lead from copper which comprises heating molten copper to a temperature in the vicinity of 2050 F., introducing an oxidizing medium into the bath, raising the temperature to the vicinity of 2160 F. to volatilize lead oxide, and keeping the surface of the bath substantially free from slag during said oxidation and volatilization.

3. The process of refining copper containing lead which comprises heating molten copper to a temperature in the vicinity of 2050 F., introducing an oxidizing medium into the bath, raising the temperature to the vicinity of 2160 F. to volatilize lead oxide, keeping the surface of the bath substantially free from slag during said oxidation and volatilization, and poling the copper under a charcoal covering to deoxidize the copper.

4. The process of refining copper containing lead which comprises heating molten copper to a temperature in the vicinity of 2050 F., introducing an oxidizing medium into the bath, raising the temperature to the vicinity of 2160 F. to volatilize lead oxide, keeping the surface of the bath substantially free from slag during said oxidation and volatilization, temporarily adding a flux to remove oxidized impurities other than lead, and poling the copper to deoxidize the copper 5. The process of removing lead from copper which comprises heating molten copper to a temperature between 2000 F. and 2160" F., introducing an oxidizing medium into the bath, raising the temperature to over 2100 F. to volatilize the lead oxide, and keeping the surface of the bath substantially free from slag during the mentioned steps.

6. The process of refining copper containing lead which comprises oxidizing and volatilizing lead in a molten copper bath free from slag, adding a slag forming material for a short period after the lead is sufiiciently removed to remove other oxidized impurities, and poling the copper to deoxidize the copper.

ALBERT T. MARCH. WALTER E. REMMERS. 

